Among conventional radio-frequency heating apparatuses of a type concerned are ones that are provided with an air guide for guiding air to a heating chamber to prevent dew condensation there and clouding of a door inner surface. The air guide is produced by shaping a metal plate-like material or a resin material into a generally U-shaped form. An illumination device is fixed to the inside of the air guide. FIG. 5 shows the configuration of a conventional radio-frequency heating apparatus.
In FIG. 5, reference numeral 1 denotes a heating chamber for housing a cooking object; 2, a door for inputting and outputting the cooking object; 3, a magnetron for supplying radio-frequency waves to the heating chamber; 4, a high-voltage transformer for supplying power to the magnetron 3; 5, a cooling fan for cooling electric parts; 6, an air guide for guiding air to the heating chamber 1; a waveguide for holding the magnetron 3 and guiding the generated radio-frequency waves to the heating chamber 1; and 8, an illumination device for illuminating the cooking object in the heating chamber 1.
In the above conventional configuration, if the air guide 6 is made of a resin material, when the illumination device 8 is attached to the air guide 6, the illumination device 8 can easily be held by the air guide 6 by using fixing nails that were formed by molding. However, if the air guide 6 is made of a metal plate, it is insufficient to hook the illumination device 8 on a bent metal portion; fixing with a vis is indispensable. However, fixing the illumination device 8 with a vis causes a problem that when the door 2 of the radio-frequency heating apparatus is opened or closed, vibration is transmitted to the filament or the like and a disconnection may occur there. This makes it necessary to use a special, stepped vis or sandwiching a buffer member between the vis and the illumination apparatus 8.
Further, the temperature tends to vary to a larger extent in metal plates than in resin materials. This results in a problem that after completion of cooking, steam that goes back from the heating chamber 1 likely condenses into dew, whereby water droplets may drop onto electric parts that are disposed under the air guide 6 to deteriorate their insulation performance.